基于增量容量曲线的锂离子电池微内短路故障诊断方法

Fault diagnosis method for microinternal short circuits in lithium-ion batteries based on incremental capacity curve

锂离子电池内短路极易引发热失控事故,有必要尽早检测出锂离子电池内短路故障。然而锂离子电池在内短路故障发展的初始阶段,短路电阻阻值较大,难以被识别诊断。本工作提出了基于锂离子电池IC曲线的电池微内短路故障诊断方法。当电池发生内短路故障时,部分充电电流会流过短路电阻而不是参与锂离子电池内部电化学反应,因此短路电池与正常电池的IC曲线会存在微小差异,可以通过计算不同短路程度锂离子电池与正常电池IC曲线之间的均方误差(MSE)进一步放大故障电池与正常电池之间的偏差,进而对锂离子电池微内短路故障进行诊断,由短路电池与正常电池在相同电压区间内充电电量的差异,开发了短路电阻的定量计算方法。模拟和实验结果表明,本工作提出的方法可对阻值达到710Ω的电池微内短路故障进行准确检测,对于短路电阻的最大估算误差为6.1%,对老化电池进行的短路实验表明该算法对于老化电池也有较强的适用性。且该算法计算复杂度低,仅需要电池低倍率充电数据即可进行短路故障诊断,时效性较强,易于实际应用。此外本工作还研究了锂离子电池在发生微内短路故障时的温升效应,结果表明短路电阻为100Ω时电池表面最大温升为4.1℃,短路电阻为710Ω时最大温升为0.4℃,电池发生微内短路故障时温升特征不明显。

Internal short circuits(ISCs)in lithium-ion batteries(LIBs)lead to thermal runaway accidents.Therefore,diagnosing ISC faults in LIBs as early as possible is essential.However,the ISC resistance of LIBs in the early ISC fault stage is large,making it difficult to diagnose the microinternal short circuit(MISC)fault of LIBs.Herein,a fault diagnosis method is proposed for the MISC fault of LIBs based on the incremental capacity(IC)curve.When an MISC fault occurs in LIBs,a part of the charging current generates ohmic heat due to the presence of the short circuit resistance rather than participating in the electrochemical reaction of the LIB to increase the battery voltage.Consequently,the IC value of a short circuit battery is higher than that of a normal battery.Mean square error of the IC values of an MISC battery and a normal battery was calculated to evaluate the deviation,thereby diagnosing the MISC fault.Based on the differences between the charging capacities of MISC and normal batteries in the same voltage range,a quantitative calculation method was developed for MISC resistance.Simulation and experimental results showed that the proposed method could accurately detect MISC faults in batteries with a resistance of 710Ω,and the maximum estimation error of the short-circuit resistance was 6.1%.Additionally,short-circuit experiments on aging batteries revealed that the proposed method was applicable for such batteries.The algorithm has low computational complexity and can be used for short-circuit fault diagnosis with just the charging data of low-rate batteries,which is easy for practical applications.The thermal effects of MISC faults in LIBs were also studied.The results demonstrated that the maximum temperature rise on the battery surface was 4.1℃when the short circuit resistance was 100Ωand 0.4℃when it was 710Ω.Temperature rise was not obvious when the MISC fault occurred in LIBs.